Scientists in the United States have successfully harnessed the captivating blue glow emitted by a sea-dwelling species of algae to create light-emitting structures. The bioluminescent single-celled organism, Pyrocystis lunula, naturally produces brief flashes of blue light, often seen as sparkling displays in waves breaking against beaches.
Inducing Sustained Glow
Giulia Brachi, a researcher at the University of Colorado Boulder, was experimenting in a darkened laboratory to find a way to make the algae emit a more sustained glow. Initially, she and her colleagues attempted to replicate the mechanical stress of waves by slowly squishing the algae, but they did not respond effectively. Other researchers have had success with mechanical stimulation, but it can be difficult to control.
Brachi then tried a different approach based on previous studies indicating that exposure to acid could trigger light production by lowering the pH level within the light-emitting part of the algae cells. When she added a slightly acidic solution to a glass lab flask containing the algae, the algae inside began to glow like living glitter. In a paper published in Science Advances, Brachi and her co-authors describe how they induced glowing for up to 25 minutes at a time.
3D Printing Glowing Shapes
The scientists encapsulated the algae within a hydrogel, a jelly-like substance made with water, and used it to 3D-print various blobby shapes, including a crescent moon that paid homage to the algae's appearance under a microscope. All the shapes glowed a strong cyan shade of blue.
Bioluminescent algae contain an enzyme called luciferase, which reacts with a light-producing compound called luciferin. These names derive from the Latin word "lucifer," meaning light bearer. According to Prof Wil Srubar, also of the University of Colorado Boulder, the algae are "pretty self-sustaining provided that they have access to seawater."
Potential Applications
Srubar suggested that this "living light" could be used for glowsticks or glowing bracelets at raves. Additionally, the algae could theoretically be embedded within biosensors that glow when they detect toxins in the environment. Prof Chris Howe of the University of Cambridge, who was not involved in the work, noted that moving from controlled lab conditions to real-world applications will be challenging, but called it "a really interesting first step." He added that for small, light-emitting devices that rely on disposable batteries, switching to bioluminescence could drastically reduce waste.
Skepticism and Remaining Mysteries
However, Anthony Campbell, a professor emeritus at the University of Cardiff, expressed skepticism about the algae's ability to survive for long in the acidic solution used in the study, which had a pH of 4—about as acidic as a tomato. "They don't like it, it stresses them," Campbell said.
One mystery remains: scientists still do not know why algae such as Pyrocystis lunula evolved to emit light in the first place. It may play a defensive role, perhaps deterring organisms that would otherwise eat the algae. Howe remarked, "To my mind, that's a fairly plausible explanation—but it's certainly not known for sure."
